ROC.lua

  roc = function(scores)
    local L,I = torch.sort(scores[{{}, 1}], 1, true)
    local labels = scores[{{},2}]:index(1,I)
    local fprev = - math.huge
    local FP = 0.0
    local TP = 0.0
    local n = labels:size(1)
    local N = n/2
    local P = n/2
    local j = 1
    local x = torch.zeros(n/2)
    local y = torch.zeros(n/2)
    for i=1,n do
      if L[i] > fprev then
        x:resize(j)
        y:resize(j)
        x[j] = FP/N
        y[j] = TP/P
        j = j + 1
      end
      if labels[i] > 0 then
        TP = TP + 1
      else
        FP = FP +1
      end
    end
    return x,y
  end